The primary objective of this project is to examine factors associated with the utilization of radiation therapy in a sample of patients with Stage IV (i.e., metastatic) non-small cell lung cancer diagnosed in selected regions of the U.S. during a period ranging from 1991 to 1996. Anecdotal reports suggest that the use of radiation therapy to palliate symptoms associated with metastatic cancer is common and that there may be substantial variation in the intensity of treatment (i.e., number of treatments). This has important cost and quality implications because studies published over the last decade suggest that shorter courses of radiation treatment may be as effective as longer courses. Although this remains controversial in the U.S., as early as 1994 clinical guidelines in the U.S. began to endorse shorter courses of therapy. We propose to use the population-based linked SEER-Medicare data set to examine patterns and determinants of the utilization of palliative radiation therapy in patients age 65 or greater diagnosed with metastatic non-small cell lung cancer between 1991 and 1996. Created by researchers at the National Cancer Institute, this data set contains clinical data on almost all patients aged 65 and older diagnosed with cancer in the eleven SEER regions that have been linked to their respective Medicare claims data. Specifically, we plan to use SEER data to identify incident cases of metastatic non-small cell lung cancer and then use the Medicare claims data to identify those patients who received radiation therapy and quantify the intensity with which they were treated. We then propose to use this information to identify factors associated with the use and intensity of treatment with radiation including patient predisposing/enabling factors, clinical factors, organizational factors and physician factors. Lastly, we plan to examine whether the frequency and intensity of the administration of treatment with palliative radiation in this patient population has changed over time.